|BREWER, MICHAEL - Texas Agrilife Research|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2018
Publication Date: 10/25/2018
Citation: Harris-Shultz, K.R., Brewer, M., Wadl, P.A., Ni, X., Wang, H. 2018. A sugarcane aphid 'Super-Clone' predominates on sorghum and johnsongrass from four US states. Crop Science. 58:2533-2541. https://doi.org/10.2135/cropsci2018.03.0151.
Interpretive Summary: The sugarcane aphid is a devastating pest on sorghum and has spread to all sorghum growing areas. Our previous research found the sugarcane aphids collected on sorghum from seven states and one U.S. territory in 2015 were all predominantly one clone. In this study we genotyped sugarcane aphids from 43 locations in eight U.S. cities in 2016 from sorghum and in 2015 and 2016 from Johnsongrass to determine if the same clone predominates on sorghum and to determine if this clone is also feeding on the invasive weed Johnsongrass. We found that indeed the same ‘superclone’ is on the 2016 samples collected from sorghum and this clone was also detected on all Johnsongrass samples collected in 2015 and 2016. Thus we have found the ‘superclone’ that feeds on sorghum also uses Johnsongrass, a weed that is pervasive in the U.S., as an alternative host.
Technical Abstract: The sugarcane aphid (SCA), Melanaphis sacchari (Zehntner) (Hemiptera: Aphididae), is the predominant pest of United States (US) grown sorghum [Sorghum bicolor (L.) Moench]. A previous study found that a single clone was prevalent on samples collected from sorghum in seven states and one territory of the US in 2015. We sought to determine if this clone was still prevalent on sorghum grown in 2016 and if this clone is also found on Johnsongrass [S. halepense (L.) Pers.]. Forty-nine SCA samples collected from sorghum and Johnsongrass at 43 locations in four states and three aphid samples from different genera (Sipha, Rhopalosiphum, and Acyrthosiphon) were genotyped with 43 SCA simple sequence repeat (SSR) markers. The predominant aphid clone found on sorghum in 2015 was again the predominant genotype in the 2016 SCA samples collected from sorghum. This same genotype was also found for the SCA samples collected from Johnsongrass in 2015 and 2016, although two samples differed by a single allele. Mixtures of this predominant genotype with three additional genotypes of SCAs were detected for three samples (excluding the control), indicating that multiple genotypes do exist in the US but at low levels. This study provides evidence that a SCA ‘super-clone’ has maintained its dominance on sorghum and it is using Johnsongrass as an alternative host.